Field of the Invention
The present invention relates to a laminated core, a VR type resolver and a production method for the laminated core.
Description of Related Art
Japanese Unexamined Patent Application Laid-open No. 2013-72673 discloses a rotor of a VR type resolver having a structure in which a protrusion for fitting into a groove formed on a shaft is formed at one portion on the inside. A rotor core of the VR type resolver has a structure in which a plurality of core forming members in a thin plate shape are laminated in an axial direction, in order to reduce iron loss. In the laminated structure, in order to secure the uniformity of magnetic characteristic in a circumferential direction, each of the thin members is laminated while gradually being rotated in a so-called “rotating lamination”. In addition, Japanese Unexamined Patent Application Laid-open No. 2003-116252 discloses a press automatic rotating lamination of iron cores for a motor having a structure in which a key groove (concavity), but not a protrusion, is formed at one portion on the inside.
In the technology described in Japanese Unexamined Patent Application Laid-open No. 2003-116252, a plurality of iron cores (thin members for forming the core) are laminated while relatively rotating, so as to position the key grooves, after the key grooves are simultaneously formed at different angular positions thereon and a punching process is carried out. In this structure, it is necessary to form the key grooves at different angular positions, and therefore, there is a problem in that the cost of used dies is increased or there is a problem in that shapes or positions of the key grooves are shifted in the rotating lamination.
In view of such circumstances, it is an object of the present invention to provide a production method for a laminated core having a structure in which a protrusion is formed on the inside or the outside which does not increase cost and in which the protrusions are prevented from shifting in rotating lamination.